1. Field of the Invention
The present invention relates to a through substrate structure and, more particularly, to a through substrate structure, a device package having the same, and methods for manufacturing the same.
2. Description of the Related Art
Recently, a vertical through connection structure in a substrate has been applied to various electronic or mechanical device packages. Research on how to form the vertical through connection structure in the substrate is conducted mainly using a silicon wafer that facilitates the formation of a vertical structure with a high aspect ratio. Typically, a process of forming a through structure with a high aspect ratio is required to reduce the size of the device and implement a high density. To this end, a deep reactive ion etching (DRIE) technique using laser or ICP equipment or a wet etching technique using a potassium hydroxide (KOH) solution is used. The laser-assisted process is a method for forming a through structure by irradiating a laser beam directly onto the surface of a silicon wafer, thereby forming a via hole of a desired size within a short time in which, however, the entrance and the inner surface of the thus formed via hole may not be smooth. Moreover, in the case of wet etching, a via hole with an inclined surface is formed along a silicon crystal surface, and thus it is very difficult to form a high density vertical through structure.
The DRIE technique can provide a high aspect ratio and a smooth surface and thus is widely used. However, voids are more likely to be formed when metal or amorphous silicon for electrical conduction is deposited in the via hole, and thus the uniformity of electrical resistance in a vertical through electrode is reduced, which is problematic. Moreover, since the silicon is deposited around a signal line, a process of forming an insulating layer, a diffusion barrier layer, and a seed layer should be performed before filing a conductive metal material in a via hole formed in a silicon wafer. However, according to the above process, many materials are deposited for signal isolation, and thus the process is very complicated, which leads to waste of time and cost, thus requiring improvement. Moreover, although an insulating film is provided, the loss of signal is significantly increased by the silicon around the signal line when applied to high frequency devices such as RF devices. That is, it can be said that the DRIE technique is not suitable for a substrate connection structure that requires high insulating performance.
As an example of another RF MEMS device packaging technique using a vertical through connection structure, a packaging technique using ceramic materials such as low temperature co-fired ceramics (LTCC) has been reported. The ceramic materials have excellent high frequency characteristics and have a multilayer structure. Thus, the ceramic materials can be used to form a thin film multilayer circuit on a single substrate and thus are widely used to manufacture high performance, high frequency semiconductor devices. However, ceramic substrates are processed mainly by machining, and thus it is relatively difficult to perform micromachining Moreover, the ceramic substrates do not have a substrate structure like silicon wafers and thus are not currently used to manufacture micro-devices through a semiconductor process. Even when RF MEMS devices are mounted in a ceramic package, a space for packaging the devices in a large ceramic package is created, and the unit devices are assembled to the ceramic package and connected to signal lines by flip-chip bonding, wire bonding, etc. Thus, it is difficult to perform wafer-level packaging, and the loss of signal transmission and the volume are increased. Further, the Korea Institute of Science and Technology (KIST) has implemented an RF MEMS packaging technique by a simple process in such a manner that a vertical through structure penetrating a glass substrate is formed by sandblasting and a signal line is formed therein by electroplating. However, during the vertical etching by sandblasting, the size of a via hole is increased, the etched surface is roughened, and the internal shape of the via hole is not uniform. Thus, the loss of signal transmission increases as the frequency increases. To this end, it is necessary to provide a vertical through connection structure, a device package having the same, and new and more effective methods for manufacturing the same.